The Germans have a great word for a tune that you cannot shake. "Ohrwurm" or earworm which gets stuck in your head. In this case it's not the last piece of music I heard on the radio before leaving home, it was a radio advert for Shop Small UK, the excellent initiative from American Express which encourages people to only shop in local stores on Saturday 6th December.
This is the advert here - the radio version is the same.

[embed]https://www.youtube.com/watch?v=kfUBY12OaYE[/embed]

Once you've listened to this then listen to this advert from British Airways back in 2011.

[embed]https://www.youtube.com/watch?v=XozHLoqwp_4[/embed]

I've not had time to research the creative source of either advert but the similarities are quite marked.